Since easySlider1.7.js extends jquery and expects it to be already defined.

Anytime you use a jquery plugin(jquery UI or whatnot), remember to reference jquery first. I looked at the examples for easySlider1.7, and the examples correctly references jquery first. A good debugging technique to use is to start with what works, i.e. the examples, and try to find the differences between what works and what doesn't. In this case the difference was that you referenced jquery after the plugin.